Heat-treating furnace



De. 29,-, 1942.- F. G. scHwALBl':

` HEAT TREATING FURNACE .Filed Feb. 29, 1940 3 Sheets-Sheet 3 tion.

Patented Dec. 29, 1942 PU NIT E D :STATES .PATENT O FFICE HEAT-TREATING FURNACE Franz G. k-Schwalbe, Toledo, Ohio Application-February 29, 1940, Serial No. 321,527

(o1. si) 3 Claims.

My invention relates to a furnace, which, if desired, may be used for heat-treating articles and for a g-reat variety of other purposes.

The invention, particularly, relates to means for preheating and directing secondary air -to be utilized ina furnace.

The invention has for its object to provide an efficient and compact means for producing heated secondary air and a controlled variable means for directing said air With reference to the burner for heating said furnace. The invention, thus, provides an eicient recuperator, which utilizes the heat of the exhaust gases from the heatng chamber, to heat secondary air and directs it to the burner to be used .in fuel combustion to heat the articles Within the furnace. The invention, also, has for its object to provide Va recuperator of a construction which lends itself readily to adaptation to any of a number of relative dispositions of the source of secondary air and the furnace heating chamber, without the use of eX- tended conduits, having no other function than conducting the heated air from the recupera-tor to the heating chamber, with a resultant loss of heat from said secondary air, during said conduc- In this connection, the invention provides one or more metallic recuperator shells located in the exhaust chamber, through which the exhaust gases of the heat-treating chamber pass, the shells being provided with means for volumetrically directing secondary air through various zones defined therein, according tothe local heat intensity of the walls in saidzones, to raise the temperature-of said secondary air and to main-- tain the parts of the Wall of the shell and the inner and outer surfaces of the said parts, at atemperature to prevent burning or warping of the walls of the shell, due to the heat of the exhaust gases transmitted to said zones. Thus, the shells may be located in proximity to the heating chamber and the overall space occupied by the furnace may be, substantially, reduced, and the draft and heat loss from the secondary' air, asit is conducted from the recuperator to the heating chamber, may be materially lessened, yas compared to that experienced in such constructions as the tower and loop type of recuperators known to the prior art.

The invention, also, has for its object to rproside and a V-shaped opposite side, having openings, and a pipe, through which unheated secondary air is distributed within the shell. The pipe'k has openings formed along one side there- 4of and is located to dispose the openings diametrically opposite to the shell openings to cause the air to ow against the curved side of said shell. The shell, also, has lateral wall portions, which curvedly jointhe curved and V-shaped sides `and are spaced-short distances from the pipe to form narrow slits, or openings, on opposite sides o f the pipe, through which the air .moves from the curved side to the opposite V-shaped side of the shell. Thus, the air is caused to spread over the surface of the shell and pass through the narrow openings between the surface of the pipe and the inner surface'of the shell, and along the opposite inner surfaces of the V-shaped side of the shell. The invention, also, provides a passageway in the wall of th-e furnace, which extends to the heat-treating chamber, and terminates in a port, in which the burner is located. The

- interior ofl the shell communicates with said passa-geway and the air is directed fromthe shell to the burner.

The invention has for a further object to provide means for controllably varying the amount, direction, and flowycharacteristic `of the secondaryair from Vthe shell and relative to the burner in the furnace heating chamber. Accordingly, the invention provides a burner, lwhich may be movably adjusted to and from a position proximate to the center of flowof the secondary air from the recuperator to the furnace heating chamber. The secondary-air may be distributed, uniformly, above the flame, or above and below the flame, by utilizing deflector and balile plates, provided by the invention. The delector of baille plates may be moved, independently of or with the burner, to Vvary the division of the second-ary air, as the burner is adjusted, with respectr to the open- A ing, to greatly lengthen the llame.

The invention may be contained in furnaces of .different forms, and, to illustrate a practical application of the invention, I have selected a heattreating furnace as an embodiment oi the invention and shall describe the selected structure hereinafter, it being understood that certain features of my invention may be usedto advantage v Without a corresponding use of other features and Without departing from the spirit of the invention, as presented in the claims. The partic-v ular structure selected is shown in the accompanyingl drawings.

Fig. l illustrates a perspective View of the heattreating'furnace. Fig. 2 illustrates a vertical section of the furnace. Fig. 3 illustrates a verticalv section of the burner and the end wall oi the heating chamber of the furnace. Fig. e illustrates a view of a horizontalsection of the burner, parts of which are shown Vbroken away to illustrate the details of the structure. Fig. 5 illustrates a longitudinal sectional view of the burner, when the burner and parts thereof are located in certain adjusted positions. Fig. 6 illustrates a longitudinal vertical section of one of the recuperator shells, shown in Fig. 1.

In the form of the furnace illustrated in the figures, I indicates the heating chamber unit and indicates the exhaust chamber unit. The units lll and l may be formed of refractory block walls I2 and |4 sheathed in sheet-metal, confining wall parts and i1, joined by suitable angle irons I8 and 20.

The upper wall 2| of the heating chamber'is formed of a plurality of closely-positioned blocks, which are connected to the supporting and conning parts of the exhaust chamber unit. The blocks of the wall 2| are slotted to form T- shaped slots 22 in their upper ends, and the sustaining frame parts of the exhaust chamber are provided with a plurality of T-shaped beams 124. The blocks, which form the upper part of the heat-treating chamber, are slidably located on the T-shaped beams 2d, and the spaces, or cracks, between the blocks, may be sealed by a suitable material 25, which may be poured into the spaces between the blocks and allowed t0 harden, thus, providing a substantially sealed cover for the heating chamber. The furnace part having the exhaust unit rests upon the upper side and end wall portions of the heating chamber unit |53. Also, on one side, the upper edge of the wall of the heating chamber is spaced a short distance from the bottom wall thereof to form the space 21, through which articles may be inserted with- 52;.

may be hooked to the frame parts 28 and theV exhaust chamber unit lifted from the heating chamber unit to enable replacement of another exhaust chamber unit or repair and replacement of the heating chamber unit.

One end of the heating chamber is providedV with a burner 3|, having a length suilicient to extend across the said end of the heating chamber. The burner comprises a shell 32, having a curved, gas reflector part 3d located on one side and curved, relatively sloping surfaces lo-4 cated on the other side, which terminate in a narrow opening 31'. The opening 31 has a length which approximates the width of the interior of the heating chamber, and the major axes of the shell are located, substantially, horizontal and disposed near the bottom of the heating chamber and beneath the space 21, through which the articles may be inserted into the heating chamber.

Gas is introduced, under pressure, through pipes 3B, into end walls 4|) of the burner. The pipes 3B communicate with a-pipe 3|, which has a plurality of spaced openings 112, through which streams of gas are directed toward the curved reflector side 34 of the burner. The inner surfaces of the burner shell, and the outer surfaces of the pipe, are located in close proximity to form narrow openings 43 and 45 at the upper and lower sides of the pipe. The gas streams are deected and divide, and move along the inner surface of the burner and through the openings 44 and 45,

formed above and below the pipe 4|, and are concentrated, by the sloping wall surfaces 35, until the mixture of the primary air and gas is projected through the opening 31, where it is ignited to form a llame, whichextends, substantially, the length of the furnace and the articles disposed within the interior of the heating chamber thereof.

The burner is located near the terminus of a passageway 41, which extends downward through an end wall 48 of the heating chamber unit. The passageway 41 terminates in an outlet 5D, which is located at right angles to the downwardly extending passageway 41, and the burner 3| is located in the outlet 50. The secondary air moves through the passageway 41 to the burner 3|. The burner may be adjustably positioned, with reference to the moving secondary air in the outlet 50, to vary the air quantity that passes above and below, to cause the gas to, progressively, burn as it proceeds the length of the heating chamber, and, thus, the flame may be greatly extended into the heating chamber and toward or beneath the articles located therein. The burner shell 32 is slidably supported on ways 46 and is adjusted by means of a pair of racks 55, which mesh with a pair of gear wheels 51. The gear wheels are located on a shaft 58, which may be operated by a suitable hand wheel 60. The racks "i are located on a baille plate 52, slidably supported on and above the pipes 38. Consequently, when the hand wheel is rotated, the baille plate 52 is moved inward until its edge 54 engages with the shell 32 and moves the shell inwardly, with reference to the outlet 50. In order to regulate the amount of secondary air,V which is directed below the burner, the wheel Bil may be rotated in the opposite direction to withdraw the baille plate 52 from engagement with the burner 3| a distance D suicient to permit the desired quantity of air to pass behind and below the burner shell. Continued rotation of the hand wheel 60 in said opposite direction causes the outer edge of the baffle plate 52 to engage the bar 5B, supported on the pipes 38, and, through the medium of said pipes 3S, draw the burner shell 32 to a retracted position, relative to the outlet 50, and, particularly, with reference to the corner 49 formed at the juncture of the passageway 41 and the outlet 59. The burner is provided with a deilector plate 5|, which projects upward, in the direction of the passageway 41, and, consequently, the air, which strikes the burner on one or the other side of the deflector plate 5|, is deflected over the top of the burner or under the burner. The deilector plate, also, forms a division point for the air, and, consequently, as ,the burner is adjusted, a varying amount of the air will pass over or under the burner. The deilector is moved with the burner, as the burner is adjusted within the outlet 5B and the deector plate 5| with reference to the corner The baille plate 52 operates to cause the air to move close about the burner 3|, and to limit the movement of an excess amount of the air beneath the burner. Thus, according to the position of the burner, and, particularly, the relative positions of the deflector plate 5| and the baille plate 52, with reference to the burner and the outlet 5B, the air quantities, which move above and below the burner, may be altered, by adjustment of the burner in said outlet and the manipulation of said baffle plate, relative to the .burner and deilector.

The passageway 41 communicates with the passageway 10 of the exhaust chamber unit The to reflect the air along the surfaces of the sides of the shell and through the narrow passageways 63, formed between the pipe and the side walls of the shells, and toward the openings 65. The exhaust chamber is provided with a passageway 10, which communicates with the shells through the openings 65, and, also, with the passageway 41, through which the secondary air passes to the burner 3l. The shells are welded to, or form a part of, a plate 1l, which separates .the exhaust gases of the burner from the secondary air that is conducted to the burner. Thus, the exhaust gases move from the heating chamber and toward the flue 12 along the surfaces of the shells, and the highly heated, secondary air passes through the passageway 10, to the passageway 41,

and over or under, or both over and under, the burner, and aids in completing the combustion of the gas of the burner, and the heat, produced thereby, is conveyed through the walls of the shells to heat the secondary air, which is, thus directed to the burner.

In order to maintain the correct heat differential, to obtain the greatest recuperative value from the exhaust gases and to prevent the walls of the shell from becoming superheated by hotter exhaust gases, the shells are divided into zones Y or chambers 14, by suitable partitioning walls 13,

and portions 15 of the pipe 61, in each of the chambers, are provided with the openings 66, so formed in area, or arranged in number, as to enable a progressive increase in the amountof air that is introduced into each of the chambers 14, more proximate the hotter zone of the exhaust chamber; that is, the point of entrance of the exhaust products into the exhaust chamber. Thus, the unheated secondary air from the source thereof may be directed to each chamber in such volume as to absorb, in the preheating of such volume of air, suflicient heat from the shell walls as would, otherwise, cause heat collapse and failure of the shell. Consequently, by the provision of said zones in the shell, it will be seen that the shell may be located in proximity to the heating chamber, whereby greater preheating elicienycy of the secondary air is experienced and the heated secondary air need be conducted but short distances from the source of heat to the place of use in the heating chamber. Further, it will be appreciated that, by varying the volumes to respective chambers, the unheated secondary air may be introduced from either end of the shell, notwithstanding the relative position of first impingement of the shell by the hotter exhaust gases, thus, enabling convenient connection of the source of supply of secondary air with the shell and without regard to the point of connection of the source with the furnace.

If desired, the article receiving space 21 may vbe cooled by a suitable water pipe 11, which may I claim:

1. In a heat exchanger, the exchanger having a chamber; a source of heated gas; means for directing fa stream of the. heated gas through the chamber; the exchanger'havinga second chamber for conducting a gas from the exchanger; a metallic shell located in the rst named chamber and in the path of the stream of heated gas the shell having a curved reflector side and an opening in the side opposite the rst named side 'communicating with the second named chamber; a source of supply of pressed air; and a pipe connected to the source of pressed air and extending through the shell and having openings for directing the pressed air into the shellv and against the said curved side to deiiectthe air toward the opening.

2. In a heatexchanger, the exchanger having a Y chamber; a source of heated gas; means for directing a stream of the heated gas through the chamber; the exchanger having a second chamber for conducting a gas from the exchanger; a

metallic shell located in the first named cham-l ber and extending along the path of the stream of heatedgas, the shell having a curved reflector side and an opening in the side opposite the first named side communicating with the second named chamber; a source of supply of pressed lair; a pipe connected to the source of pressed air and extending through the shell and having openings for directing the p-ressed air into the shell and against the said curved side to return the air toward the opening, and the shell having sides inclined to each other and extending from the ends of the 4curved reflector side and located in proximity to the pipe, and terminating at edge parts of the opening.

3. In a heat exchanger, the exchanger having a chamber; a source of heated gas; means for directing a. stream of the heated gas through the,

chamber; the exchanger having a second chamber for conducting a gas from the exchanger and a wall for separating the chambers; -a metallic shell located in the rst named chamber and extending along the path of the stream of heated gas, the interior of the shell having partitioning walls extending crosswise the direction of the stream to form a plurality of chamber parts within the shell; each chamber part of the shell having a curved reflector end and an opening communicating with the said second chamber and located in the chamber part at an end opposite the reflector end of the chamber part; a source of supply of pressed air; a pipe connected to the source of pressed air extending through the chamber parts of the shell and located intermediate the curved reflector ends and the openings and having openings for directing the pressed air into the chamber parts andagainst the said curved reflector ends of the chamber parts, each of the chamber parts having sides inclined to each other and extending from the ends of the curved reflector and located in proximity to the pipe, and terminating at opposite edge parts of the said openings communicating with the said second chamber; the area of the openings in the pipe, located in the consecutive chamber parts of the shell, varying and approximately decreasing as the temperature of the heated gases decrease.

FRANZ G. SCHWALBE. 

